With increase in capacity of information processing in recent years, various information recording technologies have been developed. In particular, the surface recording density of an HDD using a magnetic recording technology is continuously increasing at an annual rate of approximately 100%. Recently, an information recording capacity exceeding 200 gigabytes/platter with a 2.5-inch diameter of a magnetic disk for use in an HDD or the like has been demanded, and in order to satisfy such a demand, an information recording density exceeding 400 gigabits/square inch is required to be realized.
In order to achieve high recording density in a magnetic disk for use in an HDD or the like, a magnetic disk of a perpendicular magnetic recording type (a perpendicular magnetic recording disk) has been suggested in recent years. In an in-plane magnetic recording type, an easy axis of magnetization of a magnetic recording layer is oriented in a planar direction of a base surface, but in the perpendicular magnetic recording type, the easy axis of magnetization is adjusted so as to be oriented in a perpendicular direction with respect to the base surface. Compared with the in-plane magnetic recording type, the perpendicular magnetic recording type can suppress a thermal fluctuation phenomenon more at a high-density recording time, and therefore is suitable for increasing recording density.
Furthermore, as technologies that improve recording density and resistance to thermal fluctuation, suggested are magnetic recording media called a discrete track medium preventing interference of an adjacent recording track by patterning a non-magnetic track in parallel between magnetic tracks for recording, and called a bit pattern medium with arbitrary patterns artificially regularly arranged.
For patterned media, such as a discrete track medium and a bit pattern medium, suggested are a technology of forming a magnetic pattern composed of magnetic recording parts and non-recording parts by forming a magnetic recording layer on a non-magnetic base and thereafter implanting ions partially to perform demagnetization or amorphization of ion-implanted parts on the magnetic recording layer, which results in the demagnetized or amorphized parts on the magnetic recording layer serving as the non-recording parts and the magnetic recording parts magnetically separated by the non-recording parts, and a technology of forming a magnetic pattern in which a magnetic recording layer is physically separated by asperites by forming the magnetic recording layer on a non-magnetic base and thereafter milling the magnetic recording layer partially to form the asperities.
Specifically, first, a resist film is formed on a magnetic recording layer, and a stamper having a desired asperity pattern formed thereon is imprinted on the resist film to transfer the asperity pattern, or a photoresist film is formed on a magnetic recording layer, and a desired asperity pattern is formed on the photoresist film by photolithography technique. Then, ions are implanted in the magnetic recording layer via the formed recessed part, or the magnetic recording layer exposed on the surface of the recessed part is milled etching, thereby separating the magnetic recording layer.
For the patterned media, such as the discrete track medium or the bit pattern medium described above, in the case where asperities have been formed physically on the magnetic recording layer by milling, the resist film is removed, the recessed part is filled with non-magnetic substances, and thereafter planarization is performed. On the other hand, in the case where the pattern has been formed by ion implantation, the planarization is achieved only by removing the resist film. Therefore, for a method of manufacturing a patterned medium, patterning by ion implantation which has less steps and which provides higher smoothness of the base surface is attracting attention (for example, Patent Document 1).